Articles

Problems of wind speed measurements are analysed. The climatology of strong winds in the Czech Republic during the period 1961-1990 is presented. The main groups of strong winds are characterised according to their origin. The accuracy of historical written reports of strong winds and to their impacts in the pre-instrumental period are discussed. The chronology of strong damaging winds in the Czech lands from A. D. 1500-1929 is presented with a division into gales on the one hand and strong winds connected with convective storms on the other. Cases of gales of the century are described. The impact of strong winds is discussed, with special attention being paid to forest damage.

Climatic variation in the growing seasons of the 1990s was examined using 10-day values for the normalised difference vegetation index (NDVI) in five regions in Poland. The NDVI values were compared with climatic conditions, by calculating multiple correlation coefficients and regression equations for the 10-day means of NDVI on the one hand, and temperature, precipitation, and sunshine anomalies on the other, in the period between April and September. The frequency of appearance of forest fires was analysed for the same regions. The relationships between the frequency of occurrence of forest fires and NDVI values, air temperature, and precipitation were identified.

Cracow's series of nephological observations is unique in Europe. Neither the place of observations nor the methods of estimation of the degree of cloud cover nor the definition of cloud genera have changed significantly for about one hundred years. The paper presents therefore the database on cloudiness in Cracow and its possible applications on both the local and global scale.

The aim of this paper is to report extreme winter/early-spring air temperature (hereinafter temperature) anomalies in mid-latitude Europe, and to discuss the underlying forcing to these interannual fluctuations. Warm advection from the North Atlantic in late winter controls the surface-air temperature, as indicated by the substantial correlation between the speed of the surface southwesterlies over the eastern North Atlantic (quantified by a spe-cific Index Ina) and the 2-meter level air temperatures (hereinafter Ts) over Europe, 45-60°N, in winter. In mid-March and subsequently, the correlation drops drastically (quite often it is negative). This change in the relationship between Ts and Ina marks a transition in the control of the surface-air temperature: absorption of insolation replaces the warm advection as the dominant control. This forcing by maritime-air advection in winter was demonstrated in a previous publication, and is re-examined here in conjunction with extreme fluctuations of temperatures in Europe. We analyze here the interannual variability at its extreme by com-paring the warm-winter/early-spring of 1989/90 with the opposite scenario in 1995/96. For these two December-to-March periods the differences in the monthly mean air temperature in Warsaw and Torun, Poland, range above 10°C. Short-term (shorter than a month) fluctuations of air temperature are likewise very strong. We conduct pentad-by-pentad analysis of the surface-maximum air temperature (hereinafter Ттах), in a selected location, examining the dependence on Ina. The increased cloudiness and larger amounts of total precipitable water, corollary effects to the warm low-level advection in the 1989/90 winter, enhance the positive air temperature anomalies. The analysis of the ocean-surface winds is based on the Special Sensor Microwave/Imager (SSM/I) dataset; ascent rates, and over land wind data are from the European Centre for Medium-Range Weather Forecasts (ECMWF); maps of 2-m air tempera-ture, cloud cover and precipitable water are from the National Centers for Environmental Prediction (NCEP) Reanalysis.

Information on extreme rains and floods during the last millennium is gathered on the >asis of various records stretching back from modern direct instrumental records to historicil written sources, and also including proxy data based on sediments, organic remains and relef features. Among these extremes it is possible to distinguish heavy downpours, continues rains, rainy seasons, rapid snowmelts and combinations of all of them. On this basis it is in tern possible to describe phases with higher and lower frequencies of extreme rains aid floods in Europe during the last millennium in a regionally-differentiated manner. The phise of the Little Ice Age is well expressed throughout Europe, although its particular events vere never simultaneous. In the final discussion the author connect the causes of these variabiities in space and time with fluctuations in solar radiation and volcanic activity.

The paper attempts an evaluation of such climate fluctuations, as those of the Little Ice Age, from the point of view of historical data on carp culture. In the climate of Central Europe, carp growth is limited by temperature, especially in periods of unfavourable thermal conditions, and by water - in periods of drought. A tracing of the history of carp culture in the southern and western parts of Poland, where hydrological, climatic and geologi-cal conditions have been suitable for the development of fish farms, has made it possible to trace climate fluctuations since the Middle Ages onwards.